Hydrogenation and hydrogenolysis of carbohydrates with tungsten oxide promoted supported nickel catalyst

ABSTRACT

Disclosed is a process for the production of polyhydric alcohols from carbohydrates. Also disclosed is a catalyst comprising finely divided metallic nickel and finely divided tungsten oxide supported on an inert carrier wherein the metallic nickel is from 15 to 45% by weight, based on total weight of catalyst, and wherein the tungsten oxide is from 0.5 to 16% by weight, based on the total weight of catalyst.

This is a continuation of application Ser. No. 247,689, filed Apr. 26,1972, now abandoned, which in turn is a division of Ser. No. 9,059,filed Feb. 5, 1970, now U.S. Pat. No. 3,691,100.

The present invention relates to improved catalysts and to methods forthe production of such catalysts. This invention further relates to animproved process for the production of polyhydric alcohols fromcarbohydrates. More particularly, this invention relates to tungstenoxide promoted supported nickel catalysts which are useful for theproduction of polyhydric alcohols from carbohydrates.

The term "hydrogenation" as used throughout the specification andappended claims includes the addition of hydrogen to chemical compounds.

The term "hydrogenolysis" as used throughout the specification andappended claims includes the cracking of the carbon to carbon linkage ofa molecule and the addition of hydrogen to each of the fragmentsproduced by the cracking.

The term "carbohydrate" as used throughout the specification andappended claims includes monosaccharides and polysaccharides.

The term "polysaccharide" as used throughout the specification andappended claims includes those saccharides containing more than onemonosccharide unit.

A wide variety of catalysts have been proposed for the preparation ofpolyhydric alcohols from carbohydrates. The catalysts most often usedfor this purpose are the Raney nickel catalyst, such as those describedin J.A.C.S., 54, pages 4116-4117, (1932) and in U.S. Pat. No. 2,983,734,and finally divided supported nickel catalysts, such as those disclosedin U.S. Pat. No. 2,749,371. These catalysts, however, have not beenentirely satisfactory for a number of reasons. A serious disadvantage ofthese catalysts is that they are not effective for the preparation ofpolyhydric alcohols directly from polysaccharides in general. In thepreparation of hexitols from polysaccharides with these catalysts, forexample, it is usually necessary to first hydrolyze the polysaccharidesto monosaccharides prior to hydrogenation. Moreover, in the preparationof mannitol and sorbitol from monosaccharides with these catalysts, asubstantial amount of undesirable isomers such as iditol are formed. Afurther disadvantage of these catalysts is that they are not effectivefor the preparation of glycerine directly from monosaccharides. In thepreparation of glycerine from monosaccharides with these catalysts, itis necessary to carry out the hydrogenation in the presence of acracking agent, such as calcium oxide or calcium hydroxide. Thus theseprior art catalysts are not effective as hydrogenolysis catalysts.Accordingly, there is a great need in the art for a catalyst which wouldbe useful for the production of polyhydric alcohols such as glycerineand hexitols from monosaccharides and polysaccharides and which wouldnot require the presence of a hydrolyzing agent or a cracking agent.

It is an object of this invention to provide a novel catalyst.

It is another object of this invention to provide a catalyst for theproduction of polyhydric alcohols from carbohydrates.

It is another object of this invention to provide a catalysts which isuseful as either a hydrogenation catalyst or a hydrogenolysis catalyst.

It is another object of this invention to provide a catalyst which ishighly effective for the production of polyhydric alcohols directly frompolysaccharides.

It is an object of this invention to provide a process for theproduction of tungsten oxide promoted supported nickel catalysts.

It is another object of this invention to provide an improved processfor the preparation of polyhydric alcohols from carbohydrates.

It is an object of this invention to provide a process for thepreparation of hexitols directly from monosaccharides and/orpolysaccharides.

It is an object of this invention to provide a process for thepreparation of glycerine directly from monosaccharides and/orpolysaccharides without the need for an additional cracking agent.

The foregoing objects and still further objects are accomplishedaccording to the present invention by providing catalysts which comprisefinely divided metallic nickel and finely divided tungsten oxidesupported on an inert carrier wherein the amount of metallic nickel isfrom 15 to 45% by weight and the amount of tungsten in the form oftungsten oxide is from 0.5 to 16% by weight, based on the total weightof catalyst. In order to achieve the objects and advantages of thisinvention, it is essential that the catalysts contain amounts ofmetallic nickel, tungsten oxide, and inert carrier to furnish a nickeland tungsten content within the ranges defined above.

The inert carrier on which the finely divided metallic nickel and finelydivided tungsten oxide are deposited may be any of the inert materialsused heretofore for supporting hydrogenation catalysts. Illustrativeexamples of inert carriers or supports are diatomaceous earth, finelydivided silica, kieselguhr, and activated carbon. A preferred carrier isdiatomaceous earth, (e.g. Johns-Manville Hyflo Super Cel).

The catalyst of this invention may also contain small amounts of finelydivided iron supported on the inert carrier. It has been found thatsmall amounts of iron increase the activity of the catalyst. The amountof iron present in a catalyst may be up to 2.5%, preferably 0.1% to 2.0%by weight, based on the total weight of catalyst. The activity of thecatalyst may be even further increased by the presence of up to 2.0% byweight, based on the total weight of catalyst, of finely divided copper,chromium, and/or cerium.

A preferred class of catalysts of this invention comprises finelydivided metallic nickel and finely divided tungsten oxide supported onan inert carrier wherein the metallic nickel content is from 18 to 25%by weight and the tungsten content is from 2 to 12% by weight, based onthe total weight of catalyst.

The catalyst of this invention may be prepared by forming a slurry of aninert carrier in an acidic, aqueous solution of nickel nitrate andammonium tungstate [(NH₄)₂ WO₄ ], neutralizing the slurry with an alkalimetal carbonate to precipitate nickel carbonate, nickel hydroxide, andtungsten oxide onto the inert carrier, and reducing the nickel carbonateand nickel hydroxide to metallic nickel. (NH₄)₂ WO₄ may be prepared bymixing H₂ WO₄ with excess NH₄ OH on a steam bath. Catalysts containingfinely divided metallic iron, copper, chronium or cerium may be preparedby adding the nitrate of the metal to the slurry of inert carrier andaqueous solution of nickel nitrate and ammonium tungstate prior to theaddition of the alkali metal carbonate. Catalysts containing finelydivided nickel phosphate may be prepared by adding phosphoric acid tothe slurry prior to neutralization. A preferred method of preparing thecatalyst of this invention comprises: forming a slurry of inert carrierin an acidic, aqueous solution of nickel nitrate and ammonium tungstate;heating the slurry to 75° to 100°C.; adding alkali metal carbonate tothe heated slurry to precipitate nickel carbonate, nickel hydroxide, andtungsten oxide onto the surface of the inert carrier, the nickelcarbonate converting to nickel hydroxide due to the elevatedtemperature; and heating the catalyst to a temperature from 400°C. to550°C. in the presence of hydrogen to reduce the nickel hydroxide tometallic nickel.

It has now been discovered that the hydrogenation of monosaccharides,the simultaneous hydrolysis and hydrogenation of polysaccharides, thehydrogenolysis of monosaccharides, and the simultaneous hydrolysis andhydrogenolysis of polysaccharides may be conducted in a practical andeconomical manner, substantially free of degradation and isomerizationreactions, and with an almost substantially complete conversion of themonosaccharide and polysaccharide into polyhydric alcohol, by the novelmethod of incorporating the catalyst of this invention into an aqueoussolution of carbohydrate and subjecting the mixture to the action ofhydrogen under pressure at an elevated temperature.

The process of this invention may be broadly described as a method forthe preparation of polyhydric alcohols from carbohydrates whichcomprises adding a small amount of a catalyst of this invention to anaqueous solution or suspension of a carbohydrate and treating theresulting mixture with hydrogen under a pressure of about 25 to about200 atmospheres and a temperature of about 120°C. to about 250°C. untilthe conversion of the carbohydrate to polyhydric alcohol has beeneffected to the desired extent.

When the reaction is carried out at a temperature in the lower part ofthe recited temperature range, for example, 160°C., any polysaccharidepresent in the reaction mixture is hydrolyzed to its basicmonosaccharide whose aldehyde or ketone groups are then hydrogenated tohydroxyl groups to produce the desired polyhydric alcohol of themonosaccharide. Those polysaccharides having free aldehyde or ketonegroups in their molecular structure before they are subjected to theprocess of this invention may have these groups hydrogenated at the sametime as the molecule is hydrolyzed. At any rate, both hydrolysis andhydrogenation reactions appear to be taking place simultaneously whenpolysaccharides are subjected to the process of the invention, and thereaction results in the polyhydric alcohols of the basic structuralmonosaccharides. Polysaccharides composed of different monosaccharidesare hydrolyzed and hydrogenated to the polyhydric alcohol of therespective monosaccharides. Monosaccharides containing an aldehyde groupare hydrogenated almost exclusively by the process of this invention toa polyhydric alcohol containing the same number of carbon atoms, thesame space configuration of units attached to the carbon atoms, and witha hydroxyl group attached to the aldehyde carbon in place of the oxygenatom. Glucose, for example, is hydrogenated almost exclusively tosorbitol. Polysaccharides containing a ketone group in the molecule arehydrogenated to a mixture of approximately equal amounts of twodifferent polyhydric alcohols due to the isometric nature of the ketonecarbon atom. Both resulting polyhydric alcohols contain the same numberof carbon atoms as the monosaccharide with the same space configurationof units attached to the carbon atoms, but one of the polyhydricalcohols has a hydroxyl group on one side of the ketone carbon atom inplace of the oxygen atom, and the other polyhydric alcohol has thehydroxyl group on the opposite side of the ketone carbon atom in placeof the oxygen atom. Fructose, for example has a ketone group at thesecond carbon atom and the molecule is hydrogenated to approximatelyequal amounts of sorbitol and mannitol.

When the process of this invention is carried out at a temperature inthe upper part of the recited temperature range, for example, 220°C.,any polysaccharide present in the starting material is hydrolyzed to itsbasic monosaccharide. Monosaccharide present in the reaction material issimultaneously cracked and hydrogenated to produce a hydrogenolysisreaction product which contains a high percent by weight of polyolshaving a shorter carbon chain length than the monosaccharide. Thecatalyst of the present invention is dual functional in that it containsboth metallic sites for hydrogenation and acidic sites for cracking.Thus the catalyst of the present invention may be used for preparingpolyols having a shorter chain length than the monosaccharide startingmaterial. Furthermore, the catalyst of this invention does not requireprior hydrolysis of any polysaccharides present in the starting materialto monosaccharides or the presence of a cracking agent such as calciumoxide or calcium hydroxide. If desired, however, the process of thisinvention may be carried out in the presence of a cracking agent.

Illustrative examples of carbohydrates which may be converted topolyhydric alcohols in accordance with the process of this inventioninclude, for example, glucose, fructose, galactose, mannose, altrose,allose, idose, gulose, arabinose, talose, ribose, xylose, sucrose,maltose, lactose, cellobiose, malibiose, invert sugar, wood sugar,starch and starch decomposition products such as dextrine, glucosesyrups, and corn starch hydrolyzates. Mixtures of carbohydrates may alsobe used in the process of this invention.

The carbohydrate or mixture of carbohydrates to be subjected to theprocess of this invention are dissolved in water at the appropriateconcentration. Concentrations of carbohydrates from 20% to about 80% byweight are usually employed for the reaction. Carbohydrateconcentrations in the range of 40% to 70% by weight react particularlysmoothly in the reaction and such concentrations are, therefore, themore preferred for this invention. It is not necessary for thecarbohydrates to form true solutions with the water as suspensions andcolloidal solutions of carbohydrates may be used.

The amount of catalyst to be used in the process of this invention mayvary over a wide range and will depend upon the particular catalyst,carbohydrate, temperature and pressure which are employed in theprocess. In general, the higher the level of nickel and tungsten oxidein the catalyst and the higher the temperature and pressure used, theless catalyst is required. Polysaccharides tend to require a higherlevel of catalyst than do the monosaccharides. Catalyst concentrationssufficient to furnish from about 0.5% to about 3%, preferrably fromabout 0.7% to about 2%, by weight of nickel based on the weight ofcarbohydrate are suitable. It will be understood, of course, that lowerand higher concentrations of catalyst may be used if desired.

The process of the present invention is promoted by a positive hydrogenpressure and results generally improve as the pressure increases up toabout 200 atmospheres. Above that pressure little improvement is shown,at least insufficient improvement to warrant the special apparatus whichwould be required. In general, pressures between about 75 atmospheresand about 150 atmospheres have been found to give the best results. Theuse of pressure below about 75 atmospheres probably would not bewarranted in view of the better results which may be obtained in thepreferred range. It is to be understood, however, that higher and lowerpressures than those described above may be used when deemed necessaryor desirable.

The reaction temperature range of the present process extends from about120°C. to about 250°C. At temperatures lower than 120°C., the reactionis too slow to be practical. At temperatures higher than 250°C.,charring of the starting carbohydrate may occur. The particulartemperature used will depend mainly upon whether the desired product isa polyhydric alcohol containing a lower number of carbon atoms than themonosaccharidic unit of the starting carbohydrate, for example, thepreparation of glycerine from a hexose, or a polyhydric alcoholcontaining the same number of carbon atoms as the monosaccharidic unitof the starting carbohydrate, for example, the preparation of sorbitolfrom a hexose. The starting carbohydrate may be converted to apolyhydric alcohol containing the same number of carbon atoms as themonosaccharidic unit of the starting carbohydrate at temperatures up toabout 180°C. At temperatures above about 180°C., cracking of the carbonto carbon bonds starts to occur, and the amount of cracking increases asthe temperature increases until, at a temperature of about 200°C., theproduct is predominantly a polyhydric alcohol containing a lower numberof carbon atoms than monosaccharidic unit of the starting carbohydrate.Substantial cracking of carbon to carbon double bonds may be inducted attemperatures as low as about 180°C. by carrying the reaction out in thepresence of a conventional cracking agent, such as lime. Thus, attemperatures of about 180°C., the carbon chain length of the resultingpolyhydric alcohol product would depend upon whether the reaction iscarried out in the presence or absence of a cracking agent. In general,the reaction is carried out at a temperature from about 120°C. to about180°C., and preferably from about 140°C. to about 180°C., when thedesired product is a polyhydric alcohol containing the same number ofcarbon atoms as the monosaccharidic unit of the starting carbohydrate;and the reaction is carried out at a temperature from about 180°C. toabout 250°C., and preferably from about 210°C. to about 235°C., when thedesired product is a polyhydric alcohol containing a lower number ofcarbon atoms than the monosaccharidic unit of the starting carbohydrate.

The time of reaction will depend upon the specific carbohydrate orcarbohydrates being acted upon, the specific catalysts used, hydrogenpressure, temperature, and the concentration of the carbohydrate.Generally, the time may be from about 15 minutes to several hours andpreferably from about 30 minutes to about 150 minutes. However, somereactions may take longer or shorter periods of time; and, in any event,the reactions should be continued until the hydrogenation orhydrogenolysis has been completed.

The reactants may be added to the reaction chamber in any suitablemanner or in any suitable order. It is preferred to add the catalyst tothe aqueous solution or suspension of the carbohydrate and then add thehydrogen under pressure and commence heating the mixture to the desiredtemperature.

The reaction may be carried out in any suitable type of apparatus whichenables intimate contact of the reactants and control of the operatingconditions and which is resistant to the high pressures involved. Theprocess may be carried out in batch, semi-continuous, or continuousoperation.

Upon completion of the reaction, the catalyst is removed by filtrationof decantation and the polyhydric alcohols may be separated from thefiltrate by any suitable means, such as, filtration, washing,crystallization, solvent extraction, and evaporation.

In order that those skilled in the art may better understand how thepresent invention may be practiced, the following examples are given.These examples are set forth solely for the purpose of illustration andany specific enumeration of details contained therein should not beinterpreted as expressing limitations of this invention. All parts andpercentages are by weight unless otherwise stated.

EXAMPLE 1

40 grams of kieselguhr are added to a stirred solution of 178.4 grams ofNi(NO₃)₂.6H₂ O and 3.82 grams of Cu(NO₃)₂.3H₂ O dissolved in 200 ml ofdistilled water in a two-liter beaker. A milky suspension of (NH₄)₂ WO₄(prepared by mixing H₂ WO₄ and excess NH₄ OH on a steam bath) containing10.0 grams of tungsten and 180 ml of concentrated ammonium hydroxide isadded dropwise from a buret to the well-stirred slurry over a 30 minuteperiod at 80°C. The slurry is digested with stirring for 1 hour at 80°C.after which time the pH is 5.2. A solution of 60.2 grams of anhydroussodium carbonate dissolved in 150 ml water is then added dropwise from aburet over a 30 minute period. The pH is 7.5. After 30 minutes digestionat 90°C., the pH is 7.1. The green catalyst is filtered hot, washed with8 liters of hot distilled water, and dried under vacuum at 150°C. for 17hours. The green catalyst assay, as determined by laboratory analysis,is 30.9% nickel, 1.26% copper, and 8.27% tungsten in the form oftungsten oxide. The dried green catalyst is ground to pass through a 200mesh screen and then activated by passing a stream of hydrogen over itat 400°C. for 30 minutes.

EXAMPLE 2

65.0 grams of kieselguhr are added to a solution of 99.2 grams ofNi(NO₃)₂.6 H₂ O in 250 ml distilled water in a 2-liter breaker. A milkysuspension of (NH₄)₂ WO₄ (prepared by mixing 13.6 grams H₂ WO₄ and 90 mlconcentration NH₄ OH on a steam bath) containing 10.0 grams tungsten isadded dropwise from a buret over a 30 minute period at 80°C. after whichtime the pH is 5.4. A solution of 28.6 grams anhydrous sodium carbonatedissolved in 200 ml water is then added dropwise from a buret over a 30minute period. The pH is 7.4 after carbonate addition. After 30 minutesdigestion at 90°C., the pH is 7.1. The green cake is filtered hot,washed with 8 liters of hot distilled water and 500 ml acetone and driedunder vacuum at 150°C. for 2.0 hours. The dried green catalyst (98.9grams) is ground to pass through a 200 mesh screen and then activated bypassing a stream of hydrogen through it at 500°C. for 30 minutes. Thecatalyst assayed 16.8% nickel and 8.5% tungsten.

EXAMPLE 3

The procedure of Example 2 is repeated with the following change: 27.2grams H₂ WO₄ (20.0 grams tungsten) are dissolved in 90 ml concentrationNH₄ OH. The same quantities of nickel nitrate kieselguhr and sodiumcarbonate are used. The pH after addition of (NH₄)₂ WO₄ is 7.0, afteraddition of sodium carbonate 7.7, after digestion at 90°C. for 30minutes 6.7. Yield: 111.6 grams dried green catalyst (15.0% nickel,14.0% tungsten).

EXAMPLE 4

The procedure of Example 2 is followed. The pH after (NH₄)₂ WO₄ additionis 5.4, 7.3 after carbonate addition, and 6.3 after digestion. Yield:112.2 grams (19.5% nickel, 8.5% tungsten).

EXAMPLE 5

The procedure of Example 2 is followed with the exception that 6.8 gramsH₂ WO₄ (5.0 grams tungsten) are dissolved in 90 ml concentration NH₄ OH.The pH after (NH₄)₂ WO₄ addition is 5.7, after carbonate addition is8.0, after digestion 7.1. Yield: 101.2 grams green catalyst (16.9%nickel, 7.0% tungsten)

EXAMPLE 6

The procedure of Example 2 is followed with the exception that 3.4 gramsH₂ WO₄ (2.5 grams tungsten) are used. The pH after CNH₄)₂ WO₄ additionis 5.5, after carbonate 7.9, after digestion 7.1. Yield: 95.2 gramsgreen catalyst (17.2% nickel, 2.2% tungsten).

EXAMPLE 7

The procedure of Example 2 is followed with the exception that 5.1 gramsH₂ WO₄ (3.7 grams tungsten) are used. The pH after ammonium tungstateaddition 5.5, after carbonate addition 7.9, after digestion 7.1. Yield:96.1 grams green catalyst (17.2% nickel, 3.6% tungsten).

EXAMPLE 8

The procedure of Example 2 is followed with the following changes: 130grams kieselguhr, 178.4 grams Ni(NO₃)₂.6 H₂ O, 13.6 grams H₂ WO₄ (10.0grams tungsten) and 57.2 grams Na₂ CO₃ are used. The pH after (NH₄)₂ WO₄addition is 5.8, after carbonate addition it is 8.1, and after digestionit is 7.6. Yield: 201.4 grams green catalyst (16.9% nickel, 4.3%tungsten).

EXAMPLE 9

The procedure of Example 1 is followed with the exception that copper isomitted. The pH after (NH₄)₂ WO₄ addition is 5.6, after carbonateaddition 7.4, and after digestion 7.3. Yield: 108.8 grams green catalyst(31.6% nickel, 8.4% tungsten).

EXAMPLE 10

The procedure of Example 9 is followed. The pH after (NH₄)₂ WO₄ additionis 5.5, 8.1 after carbonate addition, and 7.3 after digestion. Thecatalyst, prior to reduction at elevated temperature in the presence ofhydrogen, contains 28.7% nickel and 8.6% tungsten in the form oftungsten oxide, based on the total weight of catalyst.

EXAMPLE 11

A water slurry of the reduced nickel-tungsten oxide-copper catalyst ofExample 1 containing that quantity of catalyst equivalent to 2.0%nickel, based on sugar, is heated under 500 psig hydrogen pressure to230°C. in a one-liter stainless steel autoclave agitated by a turbinerotating at 3500 rpm. When temperature equilibrium is obtained, 140grams of an agueous solution of invert sugar, containing 100 grams sugarsolids, is displaced into the antoclave from a steam lagged pressurevessel by 2000 psig hydrogen pressure. After mixing with thecatalyst-water slurry, the sugar concentration is 50%. The displacementtakes 5 seconds after which the autoclave recovers temperatureequilibrium (230°C.) in 25 seconds. Hydrogen is rapidly consumed for aperiod of 10 minutes, after which a slow, further reaction occurs. Theinitial rapid pressure drop corresponds to the hydrogenolysis of thesugar charged. The slow, secondary reaction corresponds to the furtherhydrogenolysis of hexitols. After 15 minutes at 230°C., the productcomprises 18.7% glycerine, 13.8% propylene glycol, 4.1% ethylene glycoland 0.07% sugar. The non-distillable residue consisted primarily ofsorbitol with minor amounts of mannitol, other hexitols, anhydrohexitols, and residual sugar.

When a prior art catalyst equivalent to those described in U.S. Pat. No.3,341,609 (containing 16.4% nickel, 0.81% iron, and 1.05% copper) istested under the same conditions, the product contains 4.8% glycerine,1.5% propylene glycol, 0.47% ethylene glycol, and 0.11% sugar.

EXAMPLE 12

Example 11 is repeated except that sucrose is employed as feed materialin place of the invert sugar. The product contains 19.4% glycerine,13.5% propylene glycol, 2.5 % ethylene glycol, and 0.08% sugar.

EXAMPLE 13

Example 12 is repeated with the exception that 0.5% of calcium oxide,based on the weight of sucrose, is added after 15 minutes at 230°C. Thereaction is continued for 30 minutes at 230°C. The product, after ionexchange, contains 25.5% glycerine, 13.0% propylene glycol, 4.95%ethylene glycol, and 0.05% sugar.

In the following examples a water slurry of the indicated kieselguhrsupported reduced nickel catalyst is heated under 500 psig hydrogenpressure to 180°C. in a one-liter stainless steel autoclave agitated bya turbine rotating at 3500 rpm. When temperature equilibrium isobtained, 140 gram charge of invert sugar, containing calcium hydroxideand 100 grams of sugar solids, is displaced into the autoclave from asteam lagged pressure vessel by 2000 psig hydrogen pressure. Aftermixing with the catalyst-water slurry, the sugar concentration is 50%.The displacement takes 5 seconds after which the autoclave recoverstemperature equalibrium (180°C. in 25 seconds). Hydrogen is rapidlyconsumed for a period of 3 to 10 minutes, dependent upon the nickel tosugar ratio, after which a slow, further reaction occurs. The initialrapid pressure drop corresponds to the hydrogenolysis of the sugarcharged. The slow, secondary reaction corresponds to the furtherhydrogenolysis of hexitols. After 30 minutes at 180°C. the product isremoved from the autoclave and analyzed for glycerine. The glycerinecontent of the reaction product is shown in Table I. Numbered examplesare in accordance with the process of this invention, and letteredexamples are shown for purposes of comparison.

                  TABLE I                                                         ______________________________________                                        Example                                                                              Catalyst of                                                                              Catalyst   Lime                                             Number Ex. No.    Concentration                                                                            Concentration                                                                          Glycerine                               ______________________________________                                        A      (a)        2.0%       0.50%    14.6                                    B      (b)        2.0%       0.50%    15.0                                    14     2          2.0%       0.50%    21.8                                    15     3          2.0%       0.50%    19.4                                    16     4          2.0%       0.50%    21.2                                    17     5          2.0%       0.50%    24.4                                    18     6          3.0%       1.0%     24.7                                    19     7          3.0%       1.0%     24.9                                    20     8          3.0%       1.0%     25.2                                    ______________________________________                                         (a) Kieselguhr supported reduced nickel catalyst prepared according to th     procedure of U.S. Pat. No. 3,341,609 and containing 20% nickel, 0.8% iron     0.5% copper, and 0% tungsten.                                                 (b) Kieselguhr supported reduced nickel catalyst prepared according to th     procedure of U.S. Pat. No. 3,341,609 and containing 21.6% nickel, 0.9%        iron, 3.3% copper, and 0% tungsten.                                      

EXAMPLE 21

Example 11 is repeated with the exception that the catalyst used is thereduced catalyst of Example 9. The product contains 19.7% glycerine,14.2% propylene glycol, 2.58% ethylene glycol, and 0.07% reducing sugar.

EXAMPLE 22

Example 21 is followed with the exceptions that the temperature is210°C. and the reaction time is 30 minutes. The product contains 14.1%glycerine, 6.4% propylene glycol, and 0.71% ethylene glycol.

EXAMPLE 23

The procedure of Example 22 is followed with the exceptions that thetemperature is 200°C. and the nickel-sugar-ratio is 1.0% instead of2.0%. The product contains 13.4% glycerine, 7.6% propylene glycol and0.61% ethylene glycol.

EXAMPLE 24

A water slurry of the reduced nickel-tungsten oxide catalyst of Example10 containing that quantity of catalyst equivalent to 2.0% nickel, basedon sugar, is heated under 500 psig hydrogen pressure to 160°C. in aone-liter stainless steel autoclave agitated by a turbine rotating at3500 rpm. At 160°C., a 140 gram charge of invert sugar containing 100grams of sugar solids is charged into the autoclave from a steam laggedpressure vessel by 2000 psig hydrogen pressure. After 30 minutes at160°C., the product contains 26.7% mannitol, 71.3% sorbitol, 0.05%reducing sugar, and 0.17% non-reducing sugar.

EXAMPLE 25

Example 24 is repeated with the exceptions that the catalyst employed isthe catalyst of Example 1 and that the amount of catalyst is such as tofurnish 1.0% nickel, based on the weight of sugar. After 30 minutes at160°C., the product contains 68.3% sorbitol, 27.2% mannitol, 0.09%reducing sugar, and 0.25% non-reducing sugar.

EXAMPLE 26

Example 24 is repeated with the exception that sucrose is used in placeof invert sugar. After 30 minutes at 160°C. the product contains 70.0%sorbitol, 28.4% mannitol, and 0.44% non-reducing sugar.

EXAMPLE 27

Hydrogenation of a quantity of corn starch hydrolyzate containing 100grams of sugar solids and 3% nickel catalyst based on the weight ofsugar is conducted in a two-stage process at 160°-180°C. The catalystemployed is the reduced catalyst of Example 10. The corn starchhydrolyzate used is a hydrolysis product of corn starch and containsabout 63% dextrose, about 17% disaccharide, about 4% trisaccharide,about 3% tetrasaccharides, and about 12% higher polysaccharides. Thereaction was conducted at about 160°C. and 2000 psig hydrogen pressurefor 30 minutes, and then at 180°C. for 2 hours. The product contains93.0% sorbitol, 1.3% mannitol, 1.54% hexitan, 0.04% reducing sugar, and0.25% non-reducing sugar.

EXAMPLE 28

An aqueous solution of corn starch hydrolyzate having a dextroseequivalent of 77.5 is slurried with a catalyst consisting of finelydivided metallic nickel and finely divided tungsten oxide supported onkieselguhr wherein the metallic nickel content is 41% by weight ofcatalyst and the tungsten content is 8% by weight of catalyst. Theslurry contains 50% by weight of sugar solids based on the weight of theslurry and 1.7% catalyst based on the weight of sugar. Successivebatches of this slurry are pumped at a rate of 20 liters per hour to asystem of five autoclaves connected in series. The pressure on all fiveautoclaves is maintained at 2000 psig of hydrogen, and the slurry isagitated by the addition of high pressure hydrogen. The temperature inthe first autoclave is maintained at 160°C., 170°C. in the secondautoclave, and 174°C. in each of the remaining three autoclaves. Theproduct of the fifth reactor is filtered and ion exchanged. The productcontains, based on the weight of solids, 94% sorbitol and 0% iditol.

EXAMPLE 29

An aqueous solution of invert sugar is slurried with a catalystconsisting of finely divided metallic nickel and finely divided tungstenoxide supported on kieselguhr wherein the metallic nickel content is 31%by weight and the tungsten content is 10% by weight, based on the totalweight of catalyst. The slurry contains 50% by weight of sugar based onthe weight of slurry and 1.7% by weight of metallic nickel based on theweight of sugar. Successive batches of this slurry is pumped at a rateof 8.3 liters per hour to a system of four autoclaves connected inseries. The volume of each autoclave is 8.7 liters. In all fourautoclaves, the pressure is maintained at 2000 psig of hydrogen and thetemperature at 220°C. The product of the fourth autoclave contains 32.6%glycerine.

EXAMPLE 30

The process of Example 29 is repeated with the exception that 0.5% byweight of lime, based on the weight of invert sugar, is added to thefeed slurry. The product of the fourth reactor contains 34.7% glycerine.

Although this invention has been described with reference to specificcarbohydrates and catalysts and to specific reaction conditions, it willbe appreciated that numerous other carbohydrates and catalysts may besubstituted for those specifically described and that the particularreaction conditions employed may be modified, all within the spirit andscope of this invention as defined in the appended claims.

Having described the invention, what is desired to be secured by LettersPatent is:
 1. A process for the preparation of glycerin frompolysaccharide which consists essentially of contacting an aqueoussolution of polysaccharide containing from 20% to about 80% by weight ofdissolved polysaccharide with hydrogen at a pressure between about 70atmospheres and about 150 atmospheres, at a temperature from about 180°Cto about 250°C and in the presence of a supported nickel catalystconsisting essentially of finely divided metallic nickel and finelydivided tungsten oxide supported on an inert carrier wherein the nickelcontent is from 5% to 45% by weight based on the total weight of nickel,tungsten oxide, and inert carrier and the amount of tungsten in the formof tungsten oxide is from 0.5% to 16% by weight based on the totalweight of metallic nickel, tungsten oxide, and inert carrier.
 2. Aprocess of claim 1 wherein the polysaccharide is sucrose.
 3. A processof claim 1 wherein the polysaccharide is a cornstarch hydrolyzate.
 4. Aprocess of claim 1 wherein the catalyst is a precipitated catalyst offinely divided metallic nickel, finely divided tungsten oxide, andfinely divided iron supported on an inert carrier wherein the nickelcontent is from 15% to 45% by weight based on the total weight ofcatalyst, the tungsten content is from 0.5% to 16% by weight, based onthe total weight of catalyst and the amount of iron present in thecatalyst is not more than 2.5% by weight, based on the total weight ofcatalyst.
 5. A process of claim 1 wherein the weight percent of nickelis from 18% to 25% by weight and the weight percent of tungsten is from2% to 25% by weight.
 6. A process of claim 1 wherein the catalyst isprepared by forming a slurry of an inert carrier in an acidic, aqueoussolution of nickel nitrate and ammonium tungstate, neutralizing theslurry with an alkali metal carbonate to precipitate nickel carbonate,nickel hydroxide, and tungsten oxide onto the surface of inert carrier,and reducing the nickel carbonate and nickel hydroxide to metallicnickel.
 7. A process of claim 1 wherein the temperature is from 210° to235°C.
 8. A process of claim 7 wherein the polysaccharide is sucrose.